The present invention relates to spectroscopic techniques involving luminescence, and more particularly, but not exclusively relates to the determination of lifetime of a luminophore in a light scattering medium.
There has been significant development of fluorescent and phosphorescent dyes or probes with decay kinetics dependent upon the presence or concentration of an analyte or metabolite. Accordingly, lifetime of these dyes can be measured to detect corresponding analyte(s) and/or metabolite(s) concentration. Fluorescent probes in the near-infrared range appear particularly promising for in vivo biomedical diagnostic techniques that involve external, noninvasive measurements or minimally invasive, endoscopic measurements of emitted light.
Unfortunately, quantitative lifetime measurements for such probes are often difficult to obtain in the light scattering environment typically encountered with in vivo diagnostics. Light scattering also hampers other applications of luminophore probes both inside and outside the biomedical field. Consequently, lifetime measurements are usually restricted to dilute, nonscattering solutions. Notably, even equipment used in this manner, such as a curvette to contain the dilute solution, tends to scatter light to some degree introducing an attendant inaccuracy.
Moreover, current lifetime measurement approaches have other limits—especially for fluorophore probes. For example, deconvolution of instrument function often hampers accurate time-domain measurement of lifetimes. In another example, frequency-domain approaches generally require a reference fluorophore with known lifetime characteristics in the environment of interest and at the appropriate excitation and emission wavelengths. Thus, there is a need for further contributions that address these limits and/or other drawbacks confronting this technology.